There was a trick old time photographers used to use for long exposures - they would set the camera for "Bulb" exposure,hold a card in front of the lens for afew seconds after releasing the shutter to block the light while the vibrations stopped, make a timed exposure (by counting), and then put the card over the lens again and close the shutter. Trycovering the lenswitha card in this manner until you hear the shutter open as Harriet describes. This should tell you if her solutionis correct. If you have a clear view of the sky with bright stars, a distant point source of light, or a neon advertising sign,you can useone of thoseas a target, or use a point source of light in a dark room (since there will be no more fireworks for a while).

There is definitely a structured (non-random) vibration affecting the lens - sensor orientation.

Before concluding that there is something wrong with the camera, you should conduct more tests.

I would think about the location of the tripod. Was there any vibration source that would cause a rhythmic tapping?

If you look at the first photo (6 sec exposure), you see 5 disturbances.

The second photo (3 sec exposure), you see 11 disturbances.

Especially the second is quite a high frequency.

The time itnervals between each group of pulses seem like the same if you consider the fact that the fireballs start fast and slowly decrease their speed.

Do some more tests on moving objects night time, on different camera settings and different surfaces. Listen to the camera carefully and try to note the frequency of the click sounds you say you hear during the exposure. See if they match the pattern on the pictures it takes. Of course all with no vibration reduction.

thanks guys... I'll try to do some more tests tonight or the next. About the clicking, When I am in Bulb (or any other long exposure) mode I hear click continuosly throughout the exposure... You have to be somewhat close to the camera, but I hear the shutter open then a repeated click (maybe every half second) until the shutter closes. Is that sound normal on the Pentax K10?

I don't hear a click - I hear more of a soft hum. It's the same noise I hear when I use the mirror lock-up to blow out the sensor and figure that it has something to do with the mechanism that holds the mirror up. I wouldn't call it a click, and I wouldn't have been able to hear it when there are fireworks going off. Try locking up the mirror for sensor cleaning and see if its the same noise.

I wonder if the first exposure of 6 seconds had the firework in frame the whole 6 seconds. It could actually be the same timing on the movement between the 2 firework photos. One test would be to have a moving light that you know is in frame the entire time. If it was moving at the same rate you could also tell the time between the vibrations.

I don't hear a click - I hear more of a soft hum. It's the same noise I hear when I use the mirror lock-up to blow out the sensor and figure that it has something to do with the mechanism that holds the mirror up. I wouldn't call it a click, and I wouldn't have been able to hear it when there are fireworks going off. Try locking up the mirror for sensor cleaning and see if its the same noise.

Same here.. a hum. Wonder if the mirror is slipping in and out of place?

So I called Pentax today, and I described what I told you guys and the guy told me that this could be caused by dirt on the sensor and suggests that I clean it...... I'm going to try and clean it tonight or tomorrow and I'll let you know what happens....

Ok... so I locked up the mirror to clean the sensor and looked in and noticed that the sensor is moving and it sounds just like when I am using the "auto dust removal"... Is this normal? I didn't think so, but if it is ok because what I found next isn't normal. I put the camer in bulb and removed my lens held down the shutter release, looked in and saw my sensor pulsing like it was in dust removal!!

I have a different take on this problem. Is the jitter possibly from the fireworks exploding. Maybe not the one in the air, but the one on the ground that is about ot follow this one? I know i've shot plenty of fireworks, and if you're close enough to a big display you can actually feel the explosions. Might that be the problem?